So, if an Arduino developer simply deletes the USBHost library, in subsequent development he/she is bound by LGPL only, and not anything stronger?

I thought the tricky (and controversial) thing about GPL 2 was that if you used it anywhere in your project, then your whole project falls under the licence conditions. So, everyone is certain that having _some_ GPL 2 licensed code as part of the standard Arduino 1.5 distro doesn't have a knock-on effect that means _everything_ in Auduino 1.5 is now GPL 2?

That could lead to some "uh-oh" moments... always best to be 100% clear about such issues at the outset of any development effort.